Spider communities as evaluation tools for wet heathland restoration

Over the last two centuries wet heathlands and associated habitats, such as poor fens and bogs, have suffered extensive fragmentation. Recently, large-scale projects aim to restore these rare habitats throughout Europe. To evaluate post-restoration trajectories of wet heathlands, suitable monitoring tools are urgently needed. Here, we investigated whether spider communities are useful tools for evaluating the restoration success of wet heathlands. Ordination revealed that dissimilarity in spider communities between patches of different age classes resulted mainly from vegetation cover and soil moisture. By using a functional trait-approach, we tested if the time since restoration affects trait distribution of spiders in wet heathlands. Typical wet heathland spider species were less common with increasing vegetation encroachment and lower water content. New patches were inhabited by summer active, eurytopic (non-heathland) spiders, while more typical heathland species were found in middle-aged and old patches. Our results suggest that time-related changes in vegetation structure and moistness of restored wet heathlands are clearly reflected by spider communities. Although mobile spiders quickly recolonize the restored heathlands, it takes time for typical heathland spiders to settle. Restoration measures should prevent the negative effects of a vegetation encroachment and a high density of forested edges and should rehabilitate the hydrological cycle in order to preserve rare heathland spiders. We discuss that accounting for responses of spiders provides additional information to guide wet heathlands restoration.     

Montane heathland rejuvenation by choppering—Effects on vascular plant and arthropod assemblages

Land-use changes and atmospheric nitrogen deposition have negatively affected heathland biota. Active habitat management is one possible way of counteracting the biodiversity loss associated with these habitat alterations. However, management practices for lowland heathlands often have been transferred to montane heathlands, irrespective of the differences in environmental conditions or assemblage composition. The objective of this study was to evaluate the effects of so-called choppering for the rejuvenation of montane heathland. Choppering involves chaffing and removing the largest part of the organic layer down to the mineral soil. In this study, we compared montane heathlands that were rejuvenated through the application of choppering (CHOPPER) to old-growth montane heathlands (CONTROL). Thirteen years after the rejuvenation measures had been conducted, the environmental conditions between CHOPPER and CONTROL still differed. CHOPPER was characterised by shorter vegetation (herbs/grasses and dwarf shrubs), more bare soil, less litter and higher temperatures. Although, the vascular plants and all studied arthropod groups were affected by the environmental changes, their responses were somewhat different. CHOPPER had a unique assemblage of each taxonomic group that included at least a few heathland species that mainly occurred in this treatment. However, choppering was most beneficial for vascular plants, grasshoppers and carabid beetles. As shown for lowland heathlands, choppering is also a suitable management measure for montane heathland to rejuvenate vegetation with its characteristic arthropod fauna. Due to the intact seed banks and Ericaceae root systems with their mycorrhizas, in combination with the availability of bare soil, heathland vegetation can rapidly regenerate after choppering. The keystone structures that explain the high relevance of CHOPPER, especially for vascular plants, grasshoppers and carabid beetles, are low-growing vegetation and bare soil, which result in light and warm microclimatic conditions. Based on the results of our study, we recommend choppering as a regular management measure to rejuvenate montane heathland.     

An assessment of the importance of heathlands as habitats for reptiles

SPELLERBERG, I. F., 1989. An assessment of the importance of heathlands as habitats for reptiles. Britain has a species-poor reptile fauna of six species. Although they occur in association with various types of plant communities, most species seem to be associated with heathlands. The lizard Lacerta agilis is particularly associated with heathlands but data presented here suggests that the vegetation structure of typical, undisturbed, lowland heathlands is less suitable for this species than disturbed heathland with more structural diversity.     

Interactions between fire and introduced deer herbivory on coastal heath vegetation

The coastal heathlands of the Royal National Park are impacted by both fire and herbivory by introduced deer, and to date these two factors have been dealt with independently in the management of natural areas. In recent years, there has been increasing recognition for a more integrated approach to manage these two disturbance agents. Fire and its role in Australian heathlands are well known, while impacts from introduced deer and the combined effects of fire and introduced deer are still poorly understood. In this study, we investigated the effects of fire and Javan rusa deer (Cervus timorensis) on both vegetation cover and floristics. The percentage cover of plants at different height layers and the presence/absence of individual species were recorded at sites representing two different burn histories (1993/1994 and 2000/2001) and deer presence or absence. Fire significantly reduced vegetation cover at low (<50 cm) and intermediate heights (50–100 cm), while deer presence affected grasses and sedges, and low vegetation at more recently burnt sites. Rusa deer also affected composition of the plant species assemblages, but no such effect was found for fire. Understanding the influence of each disturbance factor independently and together in the heathlands will be critical for implementing a more robust framework for future management.     

Waiting for fungi: the ectomycorrhizal invasion of lowland heathlands

1.  In England, the loss of lowland heathland, a habitat of global conservation importance, is primarily due to the invasion of birch and pine. This encroachment has been researched in depth from a plant perspective but little is known about the role of mycorrhizal fungi. In lowland heathlands the resident dwarf shrubs form ericoid mycorrhizas whereas invading trees form ectomycorrhizas. Therefore, tree encroachment into heathlands can be regarded as the replacement of a resident mycorrhizal community by an invading one.
2 . This study examined how fungi form mycorrhizas with Betula and Pinus in lowland heathlands. We addressed the question of whether there are mycorrhizal fungi that mediate invasion using a molecular ecology approach to compare the mycorrhizal inoculum potential of soil at three levels of invasion (uninvaded heathland, invaded heathland and woodland) and the fungi forming mycorrhizas on tree seedlings and trees across diverse sites.
3.  We show that in lowland heathlands: (i) seedlings have severely limited access to ectomycorrhizal fungi relative to woodlands, (ii) there are few keystone spore-dispersed ectomycorrhizal fungi that can mediate tree invasion, (iii) tree seedlings can remain non-mycorrhizal for at least one year when no inoculum is present, even near saplings, and (iv) mycorrhizal seedlings achieve greater biomass than non-mycorrhizal seedlings. Within uninvaded heathland we detected only Rhizopogon luteolus , Suillus variegatus , S. bovinus ( Pinus symbionts) and Laccaria proxima (primarily a Betula symbiont).
4. Synthesis . Overall, ectomycorrhizal inoculum in lowland heathlands is rare; most tree seedlings growing in heathland soil are not mycorrhizal due to limited spore dispersal, poorly developed spore banks and weak common mycorrhizal networks. These seedlings can persist awaiting mycorrhization to boost their growth.     

Responses of plant community mycorrhization to anthropogenic influence depend on the habitat and mycorrhizal type

Anthropogenic impact represents a major pressure on ecosystems, yet little is known about how it affects symbiotic relationships, such as mycorrhizal symbiosis, which plays a crucial role in ecosystem functioning. We analyzed the effects of three human impact types – increasing urbanity, introduction of alien plant species (alienness) and modifications in plant species distribution ranges (as a proxy for naturalness) – on plant community overall mycorrhization (including arbuscular, ecto‐, ericoid and orchid mycorrhizal plants) and arbuscular mycorrhization (indicating the degree of forming mycorrhizal symbiosis at plant community level using the relative abundance of mycorrhizal and arbuscular mycorrhizal plants, respectively). The study was carried out in three habitat types, each dominated by a distinct mycorrhizal type – ectomycorrhizal woodlands, ericoid mycorrhizal heathlands and arbuscular mycorrhizal grasslands – at the regional scale in the Netherlands. The response of community mycorrhization and arbuscular mycorrhization to anthropogenic influence showed contrasting patterns, depending on the specific aspect of human impact. Community mycorrhization responded negatively to urbanity and positively to increasing alienness, while arbuscular mycorrhization showed the reverse trend. More natural heathlands were found to be more mycorrhizal and less arbuscular mycorrhizal. The strongest responses were detected in woodlands and heathlands, while mycorrhization in grasslands was relatively insensitive to human impact. Our study highlights the importance of considering mycorrhizal symbiosis in understanding and quantifying the effects of anthropogenic influence on plant communities, especially in woodlands and heathlands.     

Management and diversity of arthropods inCalluna heathland

Heathlands, dominated byCalluna vulgaris, are located along the western seaboard of Europe. Most undergo a cyclical succession as the heather plants pass through four definable growth-phases over a period of about 30 years. Examples of upland heathlands are drawn from the North York Moors National Park, an area of Jurassic rocks in the north of England (approximately 54°25N, 0°55W). Botanical diversity is low. In a survey of 10 heathlands selected to encompass the botanical variation of the heathlands of the National Park, only 40 species of higher plants and 31 species of mosses were recorded (2.2% and 4.5% of the British flora, respectively).However, diversity of some invertebrate groups is high. Totals of 54 species of carabid beetles and 127 species of spiders were recorded (15.3% and 20.4% of the British fauna, respectively). At least two environmental gradients appear to influence the species composition of the invertebrate assemblages: a wet-dry gradient and the height of the vegetation (corresponding to the growth-phase of the heather). Experimental areas on three heathlands were burnt and cut, the traditional and more modern methods of heather management. Analysis of both the spider and beetle data indicated that the species assemblages were primarily influenced by the growth-phase of the heather. Some of the nationally rarer species are associated with the open conditions of recently-cut or burnt heathland. An altitudinal effect was also inferred since heathland at 410 m above sea level tended to be less species-rich than heathlands at ca 260 m above sea level.These results present a paradox. Although botanical diversity is extremely low, and although it is a non-natural ecosystem maintained by fire and grazing management to prevent a succession to woodland, arthropod diversity can be extremely high. The discussion focuses on the importance of upland heathlands in the conservation of insect and spider diversity, as well as on the value of these upland areas for conservation more generally.C. vulgaris is seen to be a key species on which many other species depend. One conclusion is that there is insufficient effort, nationally and especially internationally, to conserve the heathlands of Europe.     

A soil nutrient gradient in Magellanic Empetrum heathlands

The relationship of environmental and soil-nutrient variables with the floristic composition of Empetrum rubrum heathlands and related communities from northern Tierra del Fuego were studied by means of ordination techniques. A floristic gradient was found which had its axis of major variation closely related to a gradient in soil trophic status. Increases in the densities of Empetrum and other cushion plants (Bolax gummifera, Azorella lycopodioides, Pernettya pumila) along the floristic gradient were: (a) associated with a lower number of species and total cover, and greater soil erosion; (b) positively correlated with the C/N ratio and aluminium content in the soil; and (c) negatively correlated with pH, calcium content and base saturation.Climate, lithology, habitat exposure, and the history of human activity would be key factors in developing the oligotrophic conditions that favoured the establishment of different Empetrum heathlands.     

Effects of Montane Heathland Restoration on Leafhopper Assemblages (Insecta: Auchenorrhyncha)

At the beginning of the 20th century, many montane heathlands were abandoned and became subject to natural succession or afforestation by humans. Thus, the formerly large montane heathlands slowly degraded into small and isolated patches. In this study, we evaluate the influence of restoration measures on leafhopper (Auchenorrhyncha) assemblages of montane heathland ecosystems in Central Europe. Our analyses comprised three different site types that were adjacent to each other: (1) montane heathlands, (2) restoration sites, and (3) control sites. Leafhoppers showed a clear response to montane heathland restoration. Thus, after 4–5 years since implementation of restoration measurements restoration sites were characterized by the highest species richness. However, detailed analyses of leafhopper diversity, species composition, and environmental parameters on the three site types revealed that restoration sites were rather similar to control sites and significantly differing from montane heathlands. We conclude that leafhoppers are excellent bioindicators for restoration measurements because they reflected environmental differences between the three site types. Restoration measurements might only be a useful instrument to promote typical montane heathland leafhopper communities in the long run. Colonization by leafhoppers is, however, dependent on many different factors such as leafhopper mobility, vegetation structure, microclimate, and the establishment of ericaceous dwarf shrubs. Practitioners should establish a management regime (grazing and sod‐cutting) that creates a mosaic of different habitat structures and increases typical heathland vegetation, thus, favoring the colonization of typical heathland leafhoppers.     

Effects of afforestation with pines on woody plant diversity of Mediterranean heathlands in southern Spain

Open heathlands of the Strait of Gibraltar region constitute a singularvegetation type within the Mediterranean Basin owing to their high biodiversitylevels and distinct features in the biological aspects of endemism. However,they have been traditionally depicted as low profitable, tree-less, barrenlandsand have been either overlooked in conservation policies or included inextensive pine-tree afforestation programmes. Nowadays, most of the existingpine plantations are no longer exploited and have become dense pine woodlands.Here we present the results of a comparative analysis aimed to ascertain theeffects of pine stands on the structure and diversity of the woody component ofthese mediterranean heathlands. Ten sampling sites were located within thestudyarea, each consisting of two adjacent subsamples: an open heathland and aneighbouring heathland under pine-tree cover. Woody species richness andoverallshrub cover was much lower in pine-tree heath understoreys. This drop in coverwas more marked for short-lived species (seeders and withering resprouters),implying a decrease of the life-history diversity and also having noticeableconsequences in homogenizing the floristic composition of heath patches underpine trees. Heathland narrow endemics dropped significantly in pine stands,showing greater sensitivity to afforestation than nonendemics. We suggest thatthe open heathlands of the Strait of Gibraltar should be given furtherattentionin EU and IUCN conservation policies. Programmes should be implemented toprogressively eliminate abandoned pine plantations so as to restore andpreservethese highly diverse mediterranean heathlands.     

Prescribed burning of northern heathlands: <Emphasis Type="Italic">Calluna</Emphasis> <Emphasis Type="Italic">vulgaris</Emphasis> germination cues and seed-bank dynamics

The European coastal heathlands are important habitats for international conservation. Today, these low-intensity farming systems are threatened by the cessation of traditional management regimes, such as grazing and prescribed burning. In natural systems, the effects of fire on germination responses are often explained by adaptation to fire over extended periods of time. However, Northern heathlands are semi-natural systems with only a limited fire history. We investigated whether and how the keystone species in this system, Calluna vulgaris, responded to prescribed burning, based on previous findings where Calluna germinable seed-bank densities showed a pronounced peak right after fire. Our main findings were (i) an ecophysiological response to smoke; (ii) a potential explanation for this pattern, revealed by a seed-bank experiment where we managed to re-create the germination pattern experimentally by using an aqueous plant-derived smoke solution; and (iii) a history of anthropogenic use of fire and the development of heathlands in the region documented through palaeoecological investigations.     

Vegetation dynamics in Brittany heathlands after fire

The vegetation dynamics of heathlands in Brittany have been followed for three years in areas subject to fire in August 1976. The pre-fire vegetation had been analysed and mapped before its destruction. The structure of the community and the processes taking place in it (in terms of biomass, primary productivity, phenology, mineral nutrition and food value) had been examined. The redevelopment of the canopy was studied by the point-contact method along permanent line transects. This semi-quantitative study permits calculation of the relative frequency of each species and, from this, its cover. The growth form of each species and the stratification of the community are also indicated by this method. Permanent plots were also used to record changes in the vegetation, by means of a census of individuals and records of the development and growth strategy of each species. The plots were located in homogeneous areas, or on bare soil around seed parents in order to examine seed dispersal and seedling establishment. These two methods yielded detailed information on the nature of the secondary successions following fire in the heathlands of Brittany.

     

Coastal heathland vegetation is surprisingly resistant to experimental drought across successional stages and latitude

In the last decade, several major dwarf-shrub dieback events have occurred in northern European coastal heathlands. These dieback events occur after extended periods with sub-zero temperatures under snow-free conditions and clear skies, suggesting that coastal heathlands have low resistance to winter drought. As climate projections forecast increased drought frequency, intensity, and duration, coastal heathlands are likely to experience more such diebacks in the future. There are, however, few empirical studies of drought impacts and responses on plant communities in humid oceanic ecosystems. We established a drought experiment with two distinct levels of intensified drought to identify responses and thresholds of drought resistance in coastal heathland vegetation. We repeated the experiment in two regions, separated by five degrees latitude, to represent different bioclimatic conditions within the coastal heathlands' wide latitudinal range in Europe. As coastal heathlands are semi-natural habitats managed by prescribed fire, and we repeated the experiment across three post-fire successional phases within each region. Plant community structure, annual primary production, and primary and secondary growth of the dominant dwarf-shrub Calluna vulgaris varied between climate regions. To our surprise, these wide-ranging vegetation- and plant-level response variables were largely unaffected by the drought treatments. Consequently, our results suggest that northern, coastal heathland vegetation is relatively resistant to substantial intensification in drought. This experiment represents the world's wettest (2200 mm year⁻¹) and northernmost (65°8'N) drought experiment to date, thus filling important knowledge gaps on ecological drought responses in high-precipitation and high-latitude ecosystems across multiple phases of plant community succession.     

Regeneration patterns in a Central European dry heathland: effects of burning,sod-cutting and cutting

Vegetation development in dry heathlands was studied during a six-year period following experimental burning, sod-cutting and cutting in a continental area in the southern part of the Czech Republic (Podyjí National Park). Calluna vulgaris-dominated heathlands in the area were composed of uneven-aged stands and had been unmanaged for several decades. The aim of the study was testing the applicability of Western European management systems to nature conservation in a continental area. Species composition was recorded in 8 permanent plots using 25×25 cm grids, and vegetation recovery following different treatments was analysed. Calluna recovered successfully after burning. Burning dense heathlands, which contained a large amount of woody fuel, resulted in a medium-intensity fire that destroyed moss mats and litter and exposed patches of bare ground to facilitate Calluna regeneration by seed, in addition to vegetative regrowth. On the contrary, in open heathlands with patches of herbaceous vegetation, low-intensity fires which failed to expose mineral soil were more typical. Almost all Calluna regeneration was vegetative in this case, and regrowth was slower. Heathland recovery after sod-cutting to mineral soil depended on whether or not Calluna seed germination occurred in the plot. With germination, the community developed towards heathland; without towards grassland. Cutting promoted a striking increase in grass cover, which was followed by the slow recovery of Calluna. The experiments suggest that of these management systems, burning is perhaps the most appropriate in the study area. A nature conservation management system is proposed, based on sheep grazing combined with rotational burning of restricted patches.     

Plant diversity patterns in the Aljibe Mountains (S. Spain): a comprehensive account

The Aljibe Mountains are located in the southern tip of the Iberian Peninsula and have a remarkable biogeographical interest. The complete plant species list (trees, climbers, shrubs, perennial and annual herbs, ferns, lichens, bryophytes and macroscopic algae) was recorded in four 0.1 ha plots from each of the most representative community types (Quercus suber woodland, Q. canariensis forest, open heathland and Q. coccifera shrubland). Up to 119 plant species were found in total in the Q. suber woodland plot. The diversity of woody plants was analysed from 44 samples of cover (100 m line), and the herbaceous layer was explored in 200 quadrats (of 0.5 × 0.5 m). Three biodiversity components (species richness, endemism, and taxonomic singularity) were evaluated in both shrub and herbaceous layers. Open heathlands showed the highest richness of endemic species, both woody and herbaceous. The highest number of woody species was found in the evergreen Q. suber woodland, and of herbaceous species in the semi-deciduous Q. canariensis woodland. Taxonomic singularity was higher in Q. canariensis woodlands and Q. coccifera shrublands for woody species, but there were no significant differences in the herbaceous layer. Local species diversity of heathlands in this region resembles that of South African heathlands (fynbos), despite the obvious geographic and floristic distance, and contrasts with the low diversity of biogeographically closer, European temperate heathlands. The Aljibe Mountains show high diversity values for different life forms (from trees to mosses) and spatial scales (from community to region), and are rich in endemic species. Thus, this area should be recognised as a relevant unit within the Mediterranean plant diversity hot spots.     

The effects of sod cutting and additional liming on potential net nitrification in heathland soils

The effects of sod cutting, a common restoration measure to remove excess nutrients from grass-dominated heathlands, on nitrification were studied in dry and wet Dutch heathlands and in incubation experiments. In the field, soil ammonium and nitrate concentrations were measured after treatment by sod cutting, with or without additional liming. Potential net nitrification was measured by incubating soil samples of all treatments with extra ammonium in a climate chamber at pH 6. Potential net nitrification of heaths dominated by Molinia caerulea was significantly higher than that of dwarf-shrub dominated heaths. Sod cutting of the former areas significantly decreased potential net nitrification, whereas in the latter areas no differences were found. Liming of sod-cut soils greatly increased potential net nitrification and the accumulation of ammonium in the soil up to toxic concentrations could be prevented. Our results show that the combination of sod cutting and liming would create suitable soil conditions for the germination and establishment of endangered plant species of dry and wet heathlands. The success of restoration projects of these areas can thus be increased.     

The effect of topsoil removal in restored heathland on soil fauna, topsoil microstructure, and cellulose decomposition: implications for ecosystem restoration

Communities of soil macrofauna, oribatid mites, and nematodes as well as vegetation and soil chemistry were studied on twelve plots representing three replicates of the following treatments: agricultural meadow, heathland, and heathland restored either by partial or complete topsoil removal 15 years earlier. We also studied the effect of soil macrofauna on decomposition and the microstructure of the soil surface layer with litterbags in combination with the analysis of thin soil sections. The communities of soil macrofauna and oribatid mites significantly differed between agricultural meadows and heathlands. The partial and complete topsoil removal plots were more similar to heathlands with respect to macrofauna and to agricultural meadows with respect to oribatid mites. The density and diversity of soil macrofauna was higher in agricultural meadows than in heathlands; in particular, earthworms, litter transformers, root feeders, and microsaprophags were more abundant on meadows. Heathlands, in contrast, contained a much higher diversity of oribatid mites. The community structure of nematodes did not significantly differ among the treatments. Analysis of thin soil sections revealed a thick organic fermentation layer in heathlands, which was absent in agricultural meadows and only weakly developed in the topsoil removal plots. In agricultural meadows, litterbags and thin soil sections indicated that abundant macrofauna, including endogeic earthworms, were very effective in removing the litter from the soil surface and mixing it into the mineral soil. Possible effects of this soil mixing on restoration success are discussed.     

Salt spray differentially affects water status, necrosis, and growth in coastal sandplain heathland species

Sandplain heathlands are disturbance-dependent plant communities that occur infrequently in coastal areas of the northeastern United States. We hypothesize that salt spray plays a role in maintaining the composition of the heathland community by excluding salt-intolerant species close to the ocean. We examined the distributions of Solidago nemoralis, Myrica pensylvanica, Pinus rigida, and Quercus spp. in heathlands and conducted greenhouse studies to determine whether different levels of salt spray tolerance explain patterns found in the field. We found that common heathland forb and shrub species grow closer to the ocean than successional woody species. In greenhouse experiments, these species differ in their water status, necrosis, and growth responses to salt spray. The tree species P. rigida and Q. rubra are more susceptible to salt spray than the common heathland species M. pensylvanica. Our results suggest that salt spray may prevent tree species in heathlands from growing close to the ocean and therefore might be an important factor in maintaining the characteristic community composition of these dwarf shrublands in coastal habitats.     

The invertebrates of heather and heathland

WEBB, N. R., 1989. The invertebrates of heather and heathland. The southern heathlands of Great Britain have long been renowned amongst entomologists. The invertebrates fall into two groups: species which feed on heathland plants–about 40 in the case of Calluna–and a second group which depends on the particular physical conditions provided by heathland, such as hot dry sandy areas or the micro-topography of Sphagnum bogs. The ecology of representative examples will be described, and the effects of fragmentation and isolation of the heathlands on the distribution and abundance of invertebrates discussed.     

Can fire avoid massive and rapid habitat change in Italian heathlands?

Heathlands are a peculiar habitat of western Europe, and have markedly declined over the last decades. Most of the remaining fragments are now protected, but are still threatened by the encroachment of pioneer trees such as Betula pendula Roth and Populus tremula L. Prescribed fire and mechanical cutting are commonly used to control pioneer trees in northern countries, but there is little understanding of their effects towards the southern edge of the range of European heathlands. I report the results of 14 years of monitoring in a network of permanent plots located in the Vauda, one of the largest lowland heathlands in Italy. Even at high frequencies (≥3 burns in 14 years) fire did not control the expansion of pioneer trees. Actually, at frequencies of 1–2 burns in 14 years, fire stimulated the expansion of pioneer trees. The growth of pioneer trees was rapid: grassland might be completely lost from the Vauda Nature Reserve in as little as 15 years. Only yearly mechanical cutting was able to control woody plants, while in mown plots cover of C. vulgaris ranged between 7% and 19% through the study. This work shows that management of southern European lowland heathlands must be more intensive than what is usually applied in north-European contexts, because fire alone cannot control pioneer trees. Rather, combinations of prescribed fire, mowing and increasing grazing/browsing will be necessary to achieve long term conservation of heathlands where fast rates of scrub and woodland encroachment is observed.